Question

I want to use Perl’s sprintf to zerofill a variable.

sprintf("%08d", $var);

But I want to dynamically determine how many digits to zerofill.

How do I replace the “8” in sprintf("%08d", $var) with a variable called $zerofill?

Answer 1

The first argument to sprintf is just a string:

 my $zerofill = 9;
 my $number = 1000;
 my $filled = sprintf "%0${zerofill}d", $number;

Notice the braces to set apart the variable name from the rest of the string.

We have this particular problem as a slightly clever exercise in Learning Perl to remind people that strings are just strings. 🙂

However, as mobrule points out in his answer, sprintf has many features to give you this sort of flexibility. The documentation for such a seemingly simple function is quite long and there are a lot of goodies in it.